(those are images of the IBM Model M keyboard)
Problem: Given an image. Dim the image, leaving an area "normal".
- Masking (in art)
"Alpha" means "Transparent".
- 2016-03-30 - Tested 2.8.6 on Slackware 14.1
2016-03-25 - Tested 2.8.10 on Lubuntu (version not recorded)
Transparency Masking ∞
Warning: An image which already has a transparent background will have this "dimming" effect over its entire canvas!
See Dimming with a transparent background for solutions and the consequence for transparency masking on an image with a transparent background.
Windows > Single-Window Mode
You can experiment with another colour, if you like.
Don't panic! This is normal.
On the right-hand side list of layers, change the "Opacity" setting for your black layer.
Although this example uses the "Rectangle Select Tool", you could use another one if you wish.
While selecting your area, you can hold a key down for a different shape. You can make your selection roughly, and reposition it later. Yes, GIMP is weird.
shiftkey will create a square-shaped selection.
controlkey will have your (rectangular-shaped) selection centered around where you first clicked your mouse.
You can hold both
controldown at the same time, to make a square-shaped selection around where you first clicked your mouse.
If this does not look right, you can
Edit > Undoand redo some steps until you like it.
16. Your "save as" dialog will be unique to you.
Rename the file, and give it a
View the image. Hopefully your image viewer will have transparency support.
Dimming with a transparent background ∞
There is a particular concern when your original image already has transparency.
Notice the "fuzzing" around the bottom image.
You may want to edit the original image and change its background or edges. A solid background, increased feathering radius or some other setting may make a large difference.
GIMP transparent backgrounds is a tutorial on editing that now-semi-transparent background to make it fully-transparent again.
Another angle to try to solve this problem would be to have your darkness placed over only part of your image, sparing the background from any "greying" (I have not created a tutorial for this). However, the problem is still basically the same: How do you select only what you like, and still have the edges of your foreground image look good?